The trend toward lower temperatures in home and offices during cool weather, which has been brought on by the high cost of fuels and heating, has caused a resurgence in popularity of radiant electric heaters. In radiant heating, the heat in the form of infrared radiation travels directly from the source to the object, such as a person, being heated without encountering a substantial loss to the intervening air. When heat radiation emitted from the radiant heater impinges onto the skin of a person, a portion of impinging heat radiation is transmitted through the skin and interacts directly with the nerve ends and the small blood vessels of the body so as to create the sensation of warmth for the person. The heating efficacy of a heat source such as a radiant or heat lamp may be determined by ratio of the amount of radiation penetrating the skin divided by the total radiation emitted from the heat source or lamp.
It is desired that the radiation emitted by the radiant heater be preferentially selected to a desired portion of the radiation spectrum so that upon impingement of the human body its effect is substantially utilized. Such a desired portion of the radiation spectrum are wavelengths of about 1.2 to 1.7 microns.
Further, a radiant heater for residential use may typically be located within a room, such as a family room having a television, wherein the visible portion of the radiation spectrum emitted by the radiant heater may distract from the desired television viewing. Further still, the visible radiation emitted by the radiant heater serves no practical useful purpose for warming people. It is considered desirable that the visible portion of the radiation spectrum typically emitted by the radiant heater be substantially reduced.
In addition to providing radiant heat for people heating, heat lamps provide various curing functions for various industrial purposes. For example, heat lamps for curing or drying clear plastics so as to harden the clear plastics in a relatively short time are of primary importance to the packaging industry.
The curing function desired to be performed for the industrial usage is dependent, in part, on the characteristic of the medium, such as the plastic, to be cured. For example, one type of medium may be more rapidly cured when subjected to specific portions of the radiation spectrum, whereas, another type of medium may be more rapidly cured when subjected to other portions of the radiation spectrum. It is desired that the industrial art be provided with a heat lamp having means to preferentially adapt the radiation of a heat lamp to a wide variety of industrial processes while performing each of the industrial processes in a highly efficient manner.
In addition to the needs of the various industrial processes and radiant heaters, it is desired that a lamp having a radiant source be preferentially adapted to other various arts not desiring efficient heating or curing. For example, it is of particular importance to the stage and studio lighting arts that a lamp be provided that simulates a daylight color in the range of Correlated Color Temperature of 5500 degrees Kelvin. Still further, due to the increasing cost of energy it is important that the simulated daylight color be provided in an efficient manner. It is considered desirable that a lamp be provided having means so as to be adapted to the needs of the stage and studio arts.
Furthermore, in addition to the above multiple needs for people heating, industrial processing, and the stage and studio arts, various other considerations for providing various types of radiant heat and selected portions of the light spectrum may be envisioned. For example, it may be desired to provide a radiant source for infrared photography which emits substantially all of the infrared radiation while substantially reducing the visible radiation emitted by the light source.
Accordingly, objects of the present invention are, (1) to provide new and improved electric radiant heat sources or lamps which have higher efficacy in selected portions of the spectrum than what has heretofore been available, and more particularly, a lamp more effective as a radiant people heater, (2) provide a radiant heat source having means so as to be adaptive to various curing functions desired for various industrial processes, and (3) provide a lamp source having means so as to select portions of infrared and visible radiation spectrum desired to be emitted by the lamp source for various studio, stage, and other types of applications.
These and other objects of the present invention will become more apparent upon consideration of the following description of the present invention.